1. Field of the Invention
The present invention relates to a method for manufacturing a standard wafer.
2. Description of the Related Art
Today, highly integrated semiconductor devices are necessary to keep up with the rapidly developing information age. As a result, dimensions of electrical wirings in semiconductor devices are now quite small, and due to miniaturization, these semiconductor devices typically have a multi-layered structure. To electrically connect the wirings in such a multi-layered structure, contacts are formed in the semiconductor device.
As semiconductor devices have become highly integrated, the size of a contact hole used for these connections has substantially decreased, while the aspect ratio of the contact hole has greatly increased. Thus, processes for forming the contact hole have become more difficult and complex, so that failures, such as the formation of a non-opened contact hole, may frequently occur.
Generally, a non-opened contact hole is located by checking the oxide film remaining in the contact hole. A system for inspecting non-opened contact holes should have sufficient resolution in order to identify the inside of a contact hole that is of a minute size. An inspection system, however, may not be able to precisely check the non-opened contact hole, due to its resolution.
Hence, an in-line scanning electron microscope (SEM) may be typically employed for monitoring a critical dimension (CD) of the contact hole, and thus for inspecting non-opened contact holes. However, the process of using a SEM to inspect non-opened contact holes is often time-consuming, thus only several contact holes in a semiconductor substrate are selected to inspect for non-opened contact holes thereon. Accordingly, a non-opened contact hole may not be identified, e.g., it may be skipped, particularly when non-opened contact holes are locally formed in a certain portion of the semiconductor substrate that is not selected for inspection.
Recently, a method for utilizing a difference between emission intensities of secondary electrons caused by electron beams of the SEM has been developed in order to discriminate non-opened contact holes. This method may be implemented by a system known as a surface analysis system. When the electron beams are applied in a normal contact hole (“opened contact hole”) that is electrically connected to an underlying conductive material, the electrons of the electron beams pass into the conductive material. On the other hand, electrons of the electron beams accumulate along the surface of a non-opened contact hole when the electron beams are applied thereto. Thus, the beams cannot enter the underlying conductive material.
Additionally, an electric potential difference is generated between opened and the non-opened contact holes. The electric potential difference may cause differences in the amount of secondary electrons and energy distribution, as between the opened and non-opened contact holes. As a result, a brightness difference between the opened and the non-opened contact holes may appear, thus enabling the surface analysis system to identify a non-opened contact hole.
However, an inspector may not be able to authenticate the data obtained from the surface analysis system, in cases where the non-opened or opened contact holes are checked utilizing the difference between emission intensities of the secondary electrons, as caused by the electron beams of the SEM. The reliability of the inspection data obtained from the surface analysis system may be discriminated by identifying whether or not the inspection data can substantially capture a “real” (actual) failure, and by identifying whether or not the same inspection data can be obtained when an identical object is repeatedly inspected by the surface analysis system. The occurrence of the non-opened contact hole can be determined with precision only if the data generated from the surface analysis system is proven to be reliable and accurate.